For several diverse applications in various disciplines, one objective can be, e.g., to determine structural and functional features of a microscopically heterogeneous sample. A wide variety of practically important heterogeneous media, ranging from, e.g., composite materials to, e.g., porous media, e.g., to biological tissues, can be characterized by the presence of barriers (e.g., membranes in biological tissues), which can, e.g., restrict molecular diffusion. In certain cases, the prime characteristics can be, e.g., the total area of and permeability of these barriers, for example.
Direct access to the microscopic structure often can be hindered, e.g., as it may not be possible to probe the diffusion flux of molecules across a barrier in the bulk of the sample without destroying its functionality. This can be a typical situation with biological tissues. For example, the cell membrane permeability to water or ions can play an important role in cell life and functionality, yet direct access to the cell membrane can be hindered. Cell membrane permeability can be measured using optical techniques, e.g., by monitoring the minute change of the refraction index of a cell in response to absorption of water due to osmosis. Such method can be, e.g., limited to cells on a surface of a specimen, and may not be utilized non-invasively in-vivo in the bulk of an organism.
Similar issues can arise, e.g., in non-destructive testing of composite materials, as well as in quantifying properties of carbonate rocks (e.g., via rock porosity and composition) for the purpose of oil exploration, for example.
Accordingly, there may be a need to determine barrier characteristics (e.g., surface area and permeability) from a non-destructive bulk transport measurement, for example.